1. Field of the Invention
The present invention relates to a method for producing buttons, control keys, ornamental and instrument panels with fine symbols and to a component produced with the method. The described buttons are often found in instrument panels of automobiles; however, buttons of this type can generally also be employed as control keys or buttons, for example, with electronic equipment.
The following description describes the production of a button as one exemplary embodiment. However, this is not to be understood as a limitation, because the method can not only be used to process buttons and control keys, but also ornamental and instrument panels. The process of fabricating a button is described only to simplify the explanation, and the term button will hereinafter be used synonymously and interchangeably with control keys or other types of operating buttons, such as control knobs.
2. Description of the Related Art
A large number of devices with buttons are nowadays installed in the interior space of an automobile. These buttons have a plastic surface that is identified with a diagrammatic functional symbol. Until now, such buttons were entirely made of plastic which is coated with a laser-processable varnish. The functional symbols are subsequently transferred by laser engraving to the surface of the buttons. For visually enhancing of the interior of motor vehicles, it was deemed desirable to provide these buttons with a genuine metallic surface with a design that can be coordinated with the surfaces of other employed ornamental parts. It has not been possible until now to produce a button surface with this type of design.
The conventional method has the disadvantage that very fine symbols defined on the button could not be applied to metallic surfaces.
The very narrow line width of the symbol contour affects the thickness of an aluminum sheet metal, for example, that can be employed, because arbitrary thickness-width ratios could not be obtained with conventional processing methods (punching, engraving, etching). In addition, it proved difficult to precisely position the unattached interior symbol portion(s) which becomes even more difficult with narrower line widths. The requirement to coordinate the visual effect with the surfaces of surrounding components also limits the use of alternative metallization methods.
One approach has been to punch the symbols out of an aluminum plate or another metallic support plate. However, a punching process is disadvantageously coarse. When the function symbol is punched in an aluminum sheet, the line widths of the symbol contour have to be commensurate with the sheet metal thickness.
In addition, burrs resulting from the punching process have to be tolerated since they are difficult to remove. Also, residual section can remain on the button after the punching operation, in particular when areas are surrounded by a closed contour line. Therefore, care had to be taken that no unattached areas on the symbols were punched out, because such areas would otherwise fall out. This limits the shape of the punched-out sections.
It is known to cut symbols out of an aluminum support plate using a cutting beam/jet (e.g., laser beam or high-pressure water jet). However, this exhibited the same disadvantages, name a relativity coarse cutting profile with undesirable cutting edges, burrs and support webs.
If the symbol contour is cut out with a laser, then the burr and burned sections appear on the visible side of the decor.
It is also known to remove such symbols from the support plate by chemical etching. This has the disadvantage that the etched line width has to be always twice the material thickness, which prevents the application of fine symbols on a button.
Alternative metallization processes are, for example galvanic coating or coating by physical vapor deposition (PVD). However, the color and the appearance of the decor can only be adapted to the surrounding surfaces in a limited way.
In any case, after the individual inner contours of the function symbol are cut out, an accurate registration to the outer contour is required for further processing (forming operation, molding). However, the required support elements must not produce pressure points or otherwise damage the decor surface, and the position of the interior portion must not move relative to the outer contour due to mold filling during the molding phase or shrinkage during the cooling phase. In order to prevent the inner contour from being completely unattached, support webs have to be provided which can adversely affect the visual appearance of the inner contour and are therefore not acceptable for visual reasons.